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Why it’s so hard to keep bad forensics out of the courtroom

When bad science (or a bad scientist) infects the judicial process, things can go very wrong, very quickly.

“The scientist has a responsibility to let the court know there can be different interpretations. If they’re not doing that they’re not doing their duty," says Cecilia Hageman, professor of forensic science at the University of Ontario Institute of Technology. (Cole Burston / Toronto Star) | Order this photo

It was a bittersweet day for forensic science in 1998, when retired Quebec Court Justice Fred Kaufman released his report on the stunning series of blunders that led to the wrongful conviction of Guy Paul Morin, found guilty in 1984 of murdering his 9-year-old neighbour, Christine Jessop.

DNA testing cleared Morin, but Kaufman’s inquiry into what went wrong poked giant holes in the reliability of the hair and fibre comparison evidence that was the basis of the jury’s guilty finding.

Kaufman set his sights squarely on flawed forensic science, and the system that propped it up. His goal: to prevent a similar mistake from happening again.

Yet nearly 20 years later, recent scandals have once again shaken the public confidence — and renewed questions about whether the justice system has what it takes to keep junk science out of the courtroom.

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In April, the Hospital for Sick Children permanently closed its Motherisk laboratory after a Star investigation cast doubt over the reliability of the lab’s drug and alcohol hair tests, which were accepted virtually without question for years in family and criminal courts.

Typically used as proof of parental substance abuse in child protection cases, the tests played a role in the removal of an as yet unknown number of children from their families.

In the U.S., the Federal Bureau of Investigation admitted in April that hair identification testimony from its forensic scientists was flawed in 95 per cent of the 268 cases before 2000 that have been reviewed so far. The defendants were sentenced to death in 32 of the cases with flawed testimony, the Washington Post reported, and 14 have either been executed or died in jail.

These may be extreme examples of what can happen when bad science (or a bad scientist) infects the judicial process. But they expose what Alan Young, head of the Innocence Project at York University’s Osgoode Hall Law School, which works on wrongful conviction cases, calls, “one of the hidden secrets of criminal justice.”

“The bottom line is, we love science. We naively believe that because we can put a rover on Mars, we can identify people through blood samples . . . without mistake. They’re not equivalent,” Young said. “Science has done remarkable things. But I remind people that the (Space Shuttle) Challenger blew up. Not everything science does works out.”

Since DNA analysis was first used to identify the genetic fingerprints of perpetrators nearly 30 years ago, this highly specific — and thoroughly tested — technique has all but supplanted many methods that have been found to be less valid, such as hair comparison.

But even DNA analysis, which can pose challenges if the sample is not big enough or there is more than one genetic profile involved, is not infallible.

Cecilia Hageman, a professor at the University of Ontario Institute of Technology, testified in more than 100 criminal cases during the roughly 20 years she spent working as a forensic scientist at the Centre of Forensic Sciences in Toronto.

She said she is “sick and tired” of DNA evidence being upheld as “the gold standard of forensics” because the condition of a sample can skew the outcome, and there can be different interpretations of the results.

As post-conviction DNA testing has exonerated hundreds of wrongly convicted, it has revealed the inherent danger of what one New York Times op-ed column recently dubbed “the collision between the law and science.”

A big problem, says Toronto defence lawyer Alan Gold, who wrote the book on expert evidence in criminal law in Canada, is that most lawyers — along with police officers, judges and jurors — simply don’t know enough to effectively challenge scientific evidence.

“We all went to law school to avoid the math and science stuff,” Gold said. “The math and science stuff has pursued us into the courtroom, and we are not very well-equipped to deal with it.”

Although there are standards for admissibility of evidence in both Canada and the U.S., critics say the bar is not high enough.

A watershed report by the National Research Council in the U.S. in 2009 found that with the exception of DNA analysis, “no forensic method has been rigorously shown able to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source.”

Commonly used methods like shoe print analysis and fingerprinting are important tools, the report concluded, “but many need substantial research to validate basic premises and techniques.”

In cases where there are competing scientific experts, the arbiters are often jurors without scientific training, which is less than ideal, said Hageman.

“Why should it be up to a jury to listen to two testimonies and figure out which is right and which is wrong?” she said. “That’s the thing: the adversarial system doesn’t work that great when it comes to trying to get the truth out of the science.”

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